From: Ilias Apalodimas <ilias.apalodimas@linaro.org>
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: Matteo Croce <mcroce@linux.microsoft.com>,
netdev@vger.kernel.org, linux-mm@kvack.org,
Ayush Sawal <ayush.sawal@chelsio.com>,
Vinay Kumar Yadav <vinay.yadav@chelsio.com>,
Rohit Maheshwari <rohitm@chelsio.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Marcin Wojtas <mw@semihalf.com>,
Russell King <linux@armlinux.org.uk>,
Mirko Lindner <mlindner@marvell.com>,
Stephen Hemminger <stephen@networkplumber.org>,
Tariq Toukan <tariqt@nvidia.com>,
Jesper Dangaard Brouer <hawk@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Boris Pismenny <borisp@nvidia.com>, Arnd Bergmann <arnd@arndb.de>,
Andrew Morton <akpm@linux-foundation.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
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Roman Gushchin <guro@fb.com>, Hugh Dickins <hughd@google.com>,
Peter Xu <peterx@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>,
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Alexander Lobakin <alobakin@pm.me>,
Cong Wang <cong.wang@bytedance.com>, wenxu <wenxu@ucloud.cn>,
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Jakub Sitnicki <jakub@cloudflare.com>,
Marco Elver <elver@google.com>,
Willem de Bruijn <willemb@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Guillaume Nault <gnault@redhat.com>,
linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
bpf@vger.kernel.org, Matthew Wilcox <willy@infradead.org>,
Eric Dumazet <edumazet@google.com>,
David Ahern <dsahern@gmail.com>,
Lorenzo Bianconi <lorenzo@kernel.org>,
Saeed Mahameed <saeedm@nvidia.com>, Andrew Lunn <andrew@lunn.ch>,
Paolo Abeni <pabeni@redhat.com>,
Sven Auhagen <sven.auhagen@voleatech.de>
Subject: Re: [PATCH net-next v5 3/5] page_pool: Allow drivers to hint on SKB recycling
Date: Mon, 17 May 2021 14:35:44 +0300 [thread overview]
Message-ID: <YKJVEDUjmv6rRnFP@enceladus> (raw)
In-Reply-To: <074b0d1d-9531-57f3-8e0e-a447387478d1@huawei.com>
On Mon, May 17, 2021 at 07:10:09PM +0800, Yunsheng Lin wrote:
> On 2021/5/17 17:36, Ilias Apalodimas wrote:
> >>
> >> Even if when skb->pp_recycle is 1, pages allocated from page allocator directly
> >> or page pool are both supported, so it seems page->signature need to be reliable
> >> to indicate a page is indeed owned by a page pool, which means the skb->pp_recycle
> >> is used mainly to short cut the code path for skb->pp_recycle is 0 case, so that
> >> the page->signature does not need checking?
> >
> > Yes, the idea for the recycling bit, is that you don't have to fetch the page
> > in cache do do more processing (since freeing is asynchronous and we
> > can't have any guarantees on what the cache will have at that point). So we
> > are trying to affect the existing release path a less as possible. However it's
> > that new skb bit that triggers the whole path.
> >
> > What you propose could still be doable though. As you said we can add the
> > page pointer to struct page when we allocate a page_pool page and never
> > reset it when we recycle the buffer. But I don't think there will be any
> > performance impact whatsoever. So I prefer the 'visible' approach, at least for
>
> setting and unsetting the page_pool ptr every time the page is recycled may
> cause a cache bouncing problem when rx cleaning and skb releasing is not
> happening on the same cpu.
In our case since the skb is asynchronous and not protected by a NAPI context,
the buffer wont end up in the 'fast' page pool cache. So we'll recycle by
calling page_pool_recycle_in_ring() not page_pool_recycle_in_cache(). Which
means that the page you recycled will be re-filled later, in batches, when
page_pool_refill_alloc_cache() is called to refill the fast cache. I am not i
saying it might not happen, but I don't really know if it's going to make a
difference or not. So I just really prefer taking this as is and perhaps
later, when 40/100gbit drivers start using it we can justify the optimization
(along with supporting the split page model).
Thanks
/Ilias
>
> > the first iteration.
> >
> > Thanks
> > /Ilias
> >
> >
> > .
> >
>
next prev parent reply other threads:[~2021-05-17 11:35 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 16:58 [PATCH net-next v5 0/5] page_pool: recycle buffers Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 1/5] mm: add a signature in struct page Matteo Croce
2021-05-14 1:00 ` Matthew Wilcox
2021-05-14 1:34 ` Matteo Croce
2021-05-18 15:44 ` Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 2/5] skbuff: add a parameter to __skb_frag_unref Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 3/5] page_pool: Allow drivers to hint on SKB recycling Matteo Croce
2021-05-14 3:39 ` Yunsheng Lin
2021-05-14 7:36 ` Ilias Apalodimas
2021-05-14 8:31 ` Yunsheng Lin
2021-05-14 9:17 ` Ilias Apalodimas
2021-05-15 2:07 ` Yunsheng Lin
2021-05-17 6:38 ` Ilias Apalodimas
2021-05-17 8:25 ` Yunsheng Lin
2021-05-17 9:36 ` Ilias Apalodimas
2021-05-17 11:10 ` Yunsheng Lin
2021-05-17 11:35 ` Ilias Apalodimas [this message]
2021-05-13 16:58 ` [PATCH net-next v5 4/5] mvpp2: recycle buffers Matteo Croce
2021-05-13 18:20 ` Russell King (Oracle)
2021-05-13 23:52 ` Matteo Croce
2021-05-13 16:58 ` [PATCH net-next v5 5/5] mvneta: " Matteo Croce
2021-05-13 18:25 ` Russell King (Oracle)
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